Paul C Tim or Timmy is a nice low gain transparent OD if you have a british voiced amp (it sounds a bit fizzy with brigher voiced Fender style amps). I have the Tim and love it, but just picked up the Lovepedal OD11 Custom (which apparently shares the same circutry as the Tim/Timmy) and I'm really digging it as well.

A second recommendation would the the Catalinbread DLS mkIII. I had the v2 on my board for 4 years and only replaced it when the mkIII came out. Unfortunately it showed up DOA so I'm waiting for a replacement, but if it's anything like the original (internet reviews seem to place it in higher regard than the earlier versions), I highly recommend.